Question

Too much C# and too little C++ makes my mind dizzy… Could anyone remind me what this c++ declaration means? Specifically, the ending “const”. Many thanks.

protected:
     virtual ostream & print(ostream & os) const

Answer 1

A const method will simply receive a const this pointer.

In this case the this pointer will be of the const ThisClass* const type instead of the usual ThisClass* const type.

This means that member variables cannot be modified from inside a const method. Not even non-const methods can be called from such a method. However a member variable may be declared as mutable, in which case this restriction will not apply to it.

Therefore when you have a const object, the only methods that the compiler will let you call are those marked safe by the const keyword.